1. Field of the Invention
The present invention relates to a device for continuously measuring deformations in a tyre during the travel movement of a motor vehicle.
2. Description of the Related Art
During the travel movement of a motor vehicle, if the operating conditions of a tyre are known, it is possible to perform operations for controlling and adjusting the behaviour of the motor vehicle. In particular, it is useful to know whether there is skidding or no skidding of the tyre, the variation in the amount of grip available compared to a reference condition, the variation in the forces exchanged between tyre and road, so as to activate, for example, devices for preventing locking during braking (anti-skid or ABS devices), devices for preventing skidding during acceleration, active suspension systems, etc.
A device for controlling the behaviour of the tyre is described in European patent application No. 99830714.4 filed on 18 Nov. 1999 in the name of the same Applicants.
This device comprises one or more sensors which are situated at prechosen points on a tyre during its rolling travel and are capable of emitting signals indicating the spatial position assumed by these points. The signals for the position of a point on the tyre are used to determine the cyclical displacement thereof, namely the displacement pattern of the point during each revolution of the tyre, and from the latter the cyclical pattern of the speed is determined. Depending on the situation to be controlled, the longitudinal displacement (direction of forward travel of the tyre), transverse or lateral displacement (perpendicular to the direction of forward travel), vertical displacement of the point and the associated speed are taken into consideration.
The device performs a comparison between the cyclical pattern of the speed of the point detected during the i-th revolution and a cyclical pattern of a reference speed, in particular that detected during the i-th-1 revolution, i.e. immediately beforehand, and provides a signal indicating the instantaneous behaviour of the tyre. The sensors used in this device are associated with the tyre.